Method for making fuseless soft tip angiographic catheter

ABSTRACT

Thin-walled catheters are provided which have an elongated fuseless polymeric tube that is made from a single tube of extruded polymer. The elongated fuseless polymeric tube includes a body portion that had been subjected to a high temperature zone in order to solid state polymerize and enhance the mechanical stability, burst strength and kink resistance of the body portion. Also included is a tip portion of the elongated fuseless polymeric tube which was subjected to a low temperature zone to retain the initial properties of extruded polymer.

BACKGROUND OF THE INVENTION

The present invention relates to fuseless catheters having a soft tipand to their method of construction. More particularly, this inventionrelates to the construction of thin-walled angiographic catheters havingunique physical properties that are especially advantageous for theefficient passage of relatively large boluses of radiological mediumtherethrough while exhibiting a soft tip that fuselessly extends from abody having stiffness properties greater than that of the soft tip. Thefuseless aspect of the invention includes utilizing solid statepolymerization techniques.

Radiological catheters are well known for use in angiographic,diagnostic and therapeutic applications wherein it is necessary toadminister a fluid to a location within the cardiovascular system.Because these catheters are used in intravascular systems, theynecessarily must have a small outside diameter, as is appreciated in theart. In addition, radiological catheters for angiographic use should beable to deliver large boluses of radiopaque dyes or the like in arelatively short time period. These combined requirements have led theangiographic catheter industry to attempt to provide catheters having anextremely thin-walled construction while still having the ability tointroduce contrast material, chemotherapeutic agents, nutritionalmaterials, drugs and other liquid phase medically useful materials intothe human bloodstream.

Such thin-walled construction raises concerns regarding meeting strengthrequirements and burst thresholds. These concerns are especiallysignificant when it is appreciated that these strength and burstrequirements typically must be maintained when the angiographic catheteris in contact with radiological fluids and with body fluids which canhave a deleterious effect on otherwise suitable catheter shaftmaterials. Typically, in order to achieve the required high flow ratesof radiopaque fluids and the like through small caliber angiographiccatheters, such thin-walled catheters must withstand hydrostatic anddynamic pressures on the order of greater than 1,000 psi even when inthe presence of radiopaque dyes or the like.

Radiologists typically find it desirable to be able to use a catheterthat will permit injection of radiopaque dyes into arteries at a flowrate that is the maximum possible without danger of experiencingcatheter rupture. As the outside diameter of the catheter is diminishedto allow its entry into smaller vessels, the flow rates tend to bereduced because meeting such an objective typically requires a generallycorresponding reduction in the inside diameter of the catheter. Becausethe fluid must then pass through a narrower cylindrical passageway,extremely high pressures are required in order to maintain high flowrates with small-bore catheters. Consequently, in order to be able toachieve high flow rates, there is an incentive and a tendency to try tominimize the wall thickness of the catheter. This requires a catheterconstruction which exhibits a high tensile strength when extruded orotherwise formed into a catheter body.

Moreover, this high tensile strength should not be reduced because ofthe presence of a seam between the body and the tip of the catheterwhich is generally expensive to fabricate, can cause alignment problems,and could lead to fuse failure during use. Likewise, the tensilestrength of such catheters should not be significantly reduced when thecatheter is called upon to pass radiopaque dyes, or other substancessuch as bodily fluids and the like. Any such reduction in tensilestrength will restrict the amount of fluid pressure to which thecatheter device can be subjected during use, and the radiologist will belimited to the flow rate that is possible without raising a risk ofhaving the catheter burst or develop other possibly dangerous structuraldefects.

In addition, because catheters such as angiographic catheters typicallymust be able to reach distant vessels within the body without damagingor tearing the lining of the blood vessels, such catheters must havesoft tips and be flexible. Catheter tips are not subjected to high fluidpressures and should preferably be constructed of softer, more flexiblematerial than catheter bodies. Also, after catheter materials areextruded, they must be non-toxic, capable of holding an opaque fluid,non-thrombogenic, smooth-walled, and resistant to kinking. Likewise,catheter materials should be of the type that exhibit a low coefficientof friction.

It is accordingly a general object of the present invention to providefuseless, soft tip catheters and to a method of making them.

Another object of this invention is to provide catheters that allowexceptionally high flow rates therethrough even when they exhibit anexceptionally small outside diameter.

Another object of this invention is to provide catheters forangiographic use and the like which are made without a circumferentialseam or joint.

Another object of the present invention is to provide thin-walledangiographic catheters that exhibit exceptionally improved burststrength while remaining sufficiently flexible so as to permit thecatheter to reach distant vessels within the body while minimizingtrauma.

Another object of the present invention is to provide thin-walledangiographic catheters that are able to withstand high hoop stressconditions.

Another object of this invention is to provide an improved method andapparatus for making a soft-tipped angiographic catheter that has afuseless construction which exhibits enhanced burst strength whilemaintaining a soft tip.

These and other objects, features and advantages of the presentinvention will be clearly understood through a consideration of thefollowing detailed description.

SUMMARY OF THE INVENTION

It has been found that thin-walled catheters having desirableproperties, especially including high tensile strength even when passingradiopaque dyes, can be constructed from extrudable polymers that can besubjected to solid state polymerization such that its physicalproperties can be altered by exposing the extruded polymer to elevatedtemperatures. A fuseless or seamless catheter is provided which exhibitsa soft-walled tip portion by effecting solid state polymerization ofonly selected portions of the extruded polymer tube in order to therebyform a catheter which has a stiff, strong body and a pliable, atraumatictip. The body and the tip are constructed of the same polymer but havediffering physical properties. Polyamide materials are especiallysuitable polymers which undergo solid state polymerization attemperatures between the boiling point of water and the melting point ofthe polyamide material.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of this description, reference will be made to theattached drawings, wherein:

FIG. 1 is a perspective view, partially broken away, of an assembledangiographic catheter according to this invention;

FIG. 2 is a longitudinal, cross-sectional view along the line 2--2 ofFIG. 1;

FIG. 3 is a transverse cross-sectional view along the line 3--3 of FIG.1;

FIG. 3a is a transverse cross-sectional view along the line 3a--3a ofFIG. 1;

FIG. 4 is an elevational view illustrating a step according to thepresent invention; and

FIG. 5 is a somewhat schematic illustration of a treatment stepsubsequent to that shown in FIG. 4.

DESCRIPTION OF THE PARTICULAR EMBODIMENTS

FIG. 1 provides an illustration of the type of catheter, generallydesignated as 21, which can incorporate the features of the presentinvention. Catheter 21 includes an elongated fuseless polymeric tube 22having a body portion 23 and a tip portion 24. A hub member 25 ofconventional construction is secured to the elongated fuseless polymerictube 22. As can be seen in FIGS. 2, 3 and 3a, a longitudinal lumen 26extends throughout the elongated fuseless polymeric tube 22 from agenerally coaxial bore 27 in the hub member 25 to a distal orifice 28within the tip portion 24.

With more particular reference to the elongated fuseless polymeric tube22, the body portion 23 and the tip portion 24 are constructed of aunitary sheath or cylinder that was extruded in a single pass out of aprecision extrusion device. The body portion 23 is differentiated fromthe tip portion 24 primarily by virtue of their different physicalproperties. The tip portion 24 is not in any way assembled onto orsecured to the body portion 23 by any type of fusing means such as anadhesive, a solvent bond, a heat sealing procedure, a banding means orthe like. If desired, the tip portion 24 can exhibit a gradual taperingof outside diameter which decreases toward the distal orifice 28. It isalso typical that catheters of this type will exhibit a degree ofcurvature which generally includes the tip portion 24. In this regard,FIGS. 1 and 2 show a somewhat gradual curvature, while FIG. 4illustrates a more complete curvature that is known in the art as aso-called pigtail curl.

With more particular reference to FIG. 4, an elongated fuseless polymertube 32 includes a body portion 33 and a tip portion 34 which includesthe pigtail curl structure. In FIG. 4, the elongated fuseless polymertube 32 is shown placed onto a stiff wire support mandrel 35, which hasa shape which includes that of what will be the body and tip of thefinished catheter after same is affixed to a hub member 25 or the like.This support mandrel 35 is useful in imparting the desired shape to theelongated fuseless polymer tube by being shaped to conform with the typeof catheter structure that is desired. For example, the support mandrelcan be shaped as shown in FIG. 4 so as to impart a pigtail curl to thecatheter, or shaped so as to impart the type of tapered curve shown inFIGS. 1 and 2, or shaped to impart a shape typical of or required forangiographic catheters or the like, as will be understood in the art.

As will be appreciated from a consideration of FIG. 5, the supportmandrel 35 also serves to assist in distributing heat more evenly inorder to impart the desired physical properties to the body portion 23,33. With more specific reference to FIG. 5, means are shown forimparting heat energy to the extruded body portion 23, 33 whilesubstantially preventing the application of heat to the tip portion 24,34 of the elongated fuseless polymer tube 22, 32. The means illustratedin FIG. 5 includes an oven device 41 having one or more heat generatorsand one or more heat distributors 42. The support mandrel 35 and thusthe elongated fuseless polymer sheath are suspended or otherwisepositioned within the oven device 41 or the like, such as by means of ahanger assembly 43. With an arrangement such as this, the body portionof the elongated fuseless polymer sheath is subjected to the heat of theoven, such heat distribution being facilitated by wire support mandrel35. Such heat application effects a solid state polymerization of theextruded polymer throughout the body portion of the elongated fuselesspolymer sheath. This procedure can be further facilitated by includingan assembly for reducing the pressure, or for drawing a vacuum, withinthe oven device 41. Such may take the form of a vacuum pump 44 or thelike.

Means are further provided in association with the oven device 41 inorder to prevent or substantially reduce the application of heat to thetip portion 34 of the elongated fuseless polymer sheath 32. Theparticular means that are illustrated in this regard in FIG. 5 include arefrigeration unit 45 which chills water or other fluid that is pumpedinto, circulates within, and is withdrawn from an enclosure 46. Thischilled fluid provides a suitable barrier from the heat that isotherwise present within the oven device 41.

After having been treated with an assembly such as that illustrated inFIG. 5, the elongated fuseless polymer tube includes a body portion thathas undergone solid state polymerization in order to form same into aless flexible, strong body, while the tip portion which has not beenthus subjected to solid state polymerization provides a pliableatraumatic tip portion having soft, flexible properties on the order ofthose of the extruded and untreated polymer tube. Regarding the solidstate polymerization that is carried out by the heat cycle, same isbelieved to drive off water within the polymer network and to completepolymerization thereof. Application of the vacuum or reduced pressurefacilitates evaporation of moisture and decreases the time required tocarry out the degree of solid state polymerization that is desired.When, for example, the extruded polymer is a polyamide, the extrudedpolyamide can include pre-polymeric materials such as amine salts ofcarboxylic acids. When such salts are heated above their melting points,they are transformed into polyamide groups, with water molecules beingliberated. This further, solid state polymerization of the extrudedpolyamide material increases the strength of the polymer.

The elongated fuseless polymeric tube is made of an extrudable polymer.Extruded polymers include polyamides such as the nylons, as well aspolyurethanes, polyolefins, polyacetals such as Delryn, polyvinyls suchas polyvinyl chloride, and the like. Typically, the elongated fuselesspolymeric sheath will be composed of a single one of these polymers, orit can be made of multiple, coaxial layers of different polymers, forexample structures formed by coextrusion. The preferred polymers arepolyamides, which are typically condensation polymers prepared by thereaction of a diacid and a diamine having terminal carboxy and diaminegroups. Among the polyamide materials useful herein are Nylon 6, Nylon6/6, Nylon 6/9, Nylon 9, Nylon 11, Nylon 12 and a proprietary nylon,manufactured by Novoste Corporation.

Catheters according to the present invention are manufactured by firstextruding one of these polymeric materials onto an air mandrel, a wiremandrel, or other means, typically by utilizing a conventional wirecoating extrusion apparatus in order to form a continuous cylindricalextrusion. This continuous extrusion is cut to the length desired forthe elongated fuseless polymeric tube, and the forming mandrel, if asolid one is used, is removed. The elongated cut extrusion is thenplaced on a stiff wire support mandrel or the like. The polymer tube andmandrel assembly is then placed into a heat imparting means as generallydescribed herein, which maintains two distinct temperature zones. Theportion of the tube that is to form the body portion of the elongatedfuseless polymeric tube is exposed to the high temperature zone, whilethe portion of the tube that is to form the tip portion of the elongatedfuseless polymeric tube is exposed to the low temperature zone.Typically, the high temperature zone will provide a temperature that isgreater than the boiling point of water and that is less than themelting point of the polymer. Generally speaking, the low temperaturezone will be at a temperature which is less than 80° C., more preferablyat room temperature or lower.

After a period of time, typically for at least two hours or more, thesupport mandrel and elongated fuseless polymeric sheath assembly isremoved from the oven. If desired, as is often the case, the curved tipportion is thermoformed by dipping same into boiling water or the likefor a short period of time (on the order of a few minutes) and thendipping same in a cooler material (such as ice water) for another shortperiod of time (typically a few minutes). The thus completed elongatedfuseless polymeric tube is then removed from the stiff wire supportmandrel, and the catheter assembly is completed by finishing the surfaceand attaching suitable additional members such as a strain relief and aconventional needle fitting to the proximal end of the thus formedcatheter device.

Catheters according to the present invention are capable of deliveringlarge boluses of radiopaque dyes in the relatively short time periodsthat are desired during an angiographic examination or the like. Thisrequires, besides other important attributes of the invention, a bodyportion that is as thin-walled as possible. The elongated fuselesspolymeric tube, should be as thin as possible in order to permit anadequate flow of fluid through the catheter while still permittingpassage of the catheter through body vessels. A typical angiographiccatheter of the type herein described will be made of a tube so as toform a catheter having a French Size ranging from No. 2 to No. 6.

The solid state polymerization that is carried out according to thepresent invention will reduce the ability of radiopaque dyes and otherfluids which pass through the catheter, and through which the catheterpasses, from deteriorating the extrudable polymer. This provides theimportant result that the elongated fuseless polymeric sheath accordingto the present invention will retain the tensile strength and burstresistance that it exhibits in air even when the catheter assembly iscontacted for extended time periods with body fluids or radiologicalmedia, including those which contain iodine or other deleteriousmaterials.

For example, the use of the present invention has provided catheterswhich provide an increased flow rate of radiopaque fluids, suchincreases being by at least 20 percent to up to 25 percent or more forpolyamide catheters of French Size No. 4. More specifically, when usinga French Size No. 4 polyamide catheter that is not subjected to solidstate polymerization according to the present invention, it has beendifficult to attain a flow rate of on the order of 20 ml per minute.Using an otherwise identical catheter that has been subjected to solidstate polymerization according to the present invention, flow rates ofat least about 25 ml per minute, including flow rates of about 26 ml perminute, are readily attained.

The solid state polymerized catheter body according to the presentinvention protects the extruded polymer from deterioration ordetrimental change in properties upon contact with radiological fluids,water, blood and other fluids passing through or otherwise contactingthe catheter. This attribute is especially important for angiographiccatheters and the like. If, due to deterioration by a radiological fluidor the like, portions of a polyamide catheter sheath or body were tobreak off and remain in a patient's body for extended time periods,polyamides have a tendency, under those conditions, to depolymerize andrelease monomers which can raise toxicity concerns. Such concerns aresubstantially eliminated by the present invention. Also, polyamideswhich are extruded and not solid state polymerized tend to absorb waterfrom contact with blood or tissue, and the absorbed water can lead toplasticizing of the polyamide polymer. When a radiological medium suchRenographin 76 (supplied by Squibb) or Hypaque is brought into contactwith a polymer that has not been solid state polymerized, it canplasticize or soften the polymer, which results in a reduction of itstensile strength and a reduction of its flexural modulus.

The following examples illustrate catheters according to the presentinvention, as well as their preferred method of manufacture.

EXAMPLE 1

A proprietary polyamide material, which is manufactured by NovosteCorporation, was extruded through a precision extruder into tubingsuitable for use in preparation of an angiographic catheter. Theextruded tubing was cut to a desired length and positioned on astainless steel mandrel having a pigtail curl at the distal end portionthereof. This assembly was then placed into an oven device generally inaccordance with FIG. 5 which maintains two different temperature zones.The upper or body portion was maintained at a temperature of 120° C.,while the lower portion comprising a three inch tip portion whichcontains the pigtail shape was maintained at 10° C. in chilled water.After two and one-half hours, the catheter was removed from the oven,and the tip assembly was thermally set by immersing the pigtail sectionin boiling water for three minutes. The assembly was then chilled in icewater for two minutes, after which the mandrel was removed, and thecatheter was fully assembled by adding a hub member and the like.

The catheter thus formed was of French Size No. 4. The static burstpressure was measured at 1,400 psi in water. An otherwise substantiallysimilarly manufactured French Size No. 4 Novolon catheter which was notsubjected to the solid state polymerization procedure within the ovendevice exhibited a static burst pressure of approximately 1,000 psi inwater. This represents an approximately 40 percent increase achieved bythe present invention.

The tip of the catheter, which was exposed to the low temperature zone,was noticeably more pliable and bends further under load before kinkingoccurs than does the body portion or shaft of the catheter device madeaccording to this example.

EXAMPLE 2

A catheter is made generally in accordance with Example 1. However,after the extruded Novolon material is cut to the desired length, thedistal tip portion thereof is tapered, and holes are punched near thedistal tip in order to assist in dispersion of the injecting media whenthe device is used as an angiographic catheter. Also, the hightemperature zone is maintained at approximately 125° C., while the lowtemperature zone is maintained at room temperature or cooler.

EXAMPLE 3

Nylon 6/9 was extruded into French Size No. 4 catheter tubes having anouter diameter of 0.054 inch, an inner diameter of 0.040 inch and a wallthickness of 0.007 inch and this tube was cut to a length suitable forcatheter use. The cut tube is inserted over a stiff wire mandrel havinga configuration desired for the finished catheter product. This tube andstiff wire support mandrel are heated to a temperature greater than 100°C. and less than the melting point of the nylon polyamide in order toeffect solid state polymerization of the polyamide tube. When the thustreated catheter tube is assembled into a catheter and used to injectRenographin 76, better thromboresistant properties are exhibited whencompared with untreated Nylon 6/9 catheters exhibiting the same tubedimensions. They do not soften, and they will retain their in-air burststrength of 1,200 psi, a 20 percent improvement over the burst strengthof such untreated catheters that deliver boluses of Renographin 76. Inaddition, the thus treated catheter tubes will have an ultimateelongation at yield of more than 100 percent and a flexural modulus ofbetween about 100,000 and 400,000 psi. Furthermore, the thus treatedcatheters meet other criteria required and desired by radiologists inthat they are non-toxic, are able to be filled with opaque medium, arenon-thrombogenic, and exhibit low kinkability.

EXAMPLE 4

A polyurethane is prepared from 1,4-bisphenol isocyanate,polytetramethylene glycol having a molecular weight of about 1,000, and1,4-butene diol in a manner that is generally known. The preparation iscarried out so that the polyurethane exhibits an isocyanate-to-hydroxylratio of 0.98. The resulting polyurethane slab is peletized and extrudedinto a catheter tube having an inner diameter of 0.045 inch and an outerdiameter of 0.075 inch. This catheter, which has a wall thicknessgreater than that of the catheter of Example 3, will have an ultimatetensile strength at yield (burst strength) of approximately 8,000 psi,an ultimate elongation at yield of more than 100 percent, and a flexuralmodulus of between about 100,000 and 400,000 psi after heat treatmentaccording to conditions specified relative to this invention. When thethus treated polyurethane tubing is assembled into a catheter, same willhave a burst strength for passage of radiographic medium that is 20percent greater than catheters having tubing of the same sizing madefrom polyurethane which is not so treated.

EXAMPLE 5

Nylon 6/6 is extruded into catheter tubes with an outer diameter of0.054 inch, an inner diameter of 0.04 inch, and a wall thickness of0.007 inch. When this tubing is not treated according to the presentinvention and is assembled into an angiographic catheter, same willdemonstrate a burst strength of 1,300 psi in air, 1,100 psi in water and900 psi in Renographin 76 radiopaque dye. Tubes treated according to thepresent invention and assembled into catheters will exhibit a burststrength in radiopaque dye of 1,300 psi, which is substantially the sameburst strength in air of catheters made with untreated tubes.

It will be understood that the embodiments of the present inventionwhich have been described are merely illustrative of some of theapplications of the principles of the present invention. Numerousmodifications may be made by those skilled in the art without departingfrom the true spirit and scope of the invention.

I claim:
 1. The method for making elongated, fuseless, polymeric tubinghaving a first portion which exhibits kink and burst resistance and asecond portion which is more pliable than the first portion, the methodcomprising:extruding an elongated, fuseless, polymeric tube having alumen therewithin; heating a first portion of the elongated polymerictube to an elevated temperature greater than 100° C. but less than themelting point of the polymeric tube for a sufficient time to effectsolid state polymerization of the first portion; maintaining a secondportion of the elongated polymeric tube at a temperature lower than thefirst portion during the time said first portion is being heated, so asto inhibit solid state polymerization in the second portion and thusprovide a second portion which is more pliable than the first portion.2. The method according to claim 1 further including the steps ofplacing the elongated polymeric tube on a support mandrel prior toheating, and subsequently removing the elongated polymeric tube from thesupport mandrel.
 3. The method according to claim 1 wherein said lowertemperature of the second portion is sufficiently low to substantiallyprevent solid state polymerization of the second portion.
 4. The methodaccording to claim 1, wherein said lower temperature of the secondportion is less than 80° C.
 5. The method according to claim 1 whereinsaid lower temperature of the second portion is room temperature orbelow.
 6. The method according to claim 1 wherein the step of heatingthe first portion includes subjecting the first portion of the elongatedpolymeric tube to a temperature zone greater than 100° C. but less thanthe melting point of the polymeric tube.
 7. The method according toclaim 6 wherein the second portion of the elongated tube is subjected toa lower temperature zone than said first portion.
 8. The methodaccording to claim 1 wherein the step of heating includes subjecting thefirst portion of the elongated polymeric tube to an elevated temperaturezone greater than 100° C. but less than the melting point of thepolymeric tube and wherein the elevated temperature zone exhibits apressure that is substantially lower than atmospheric pressure.
 9. Themethod according to claim 2 wherein the support mandrel is a heatconductor which assists in distributing heat to the first portion of thepolymeric tube.
 10. The method according to claim 1 wherein thepolymeric tube is formed of polyamide material.
 11. The method accordingto claim 1 including the steps of:forming the second portion of theelongated polymeric tube into a selected shape; heating the secondportion to an increased temperature for a sufficient period of time suchthat the second portion will retain the selected shape when cooled, saidincreased temperature and period of time being sufficient to causesubstantial solid state polymerization of the second portion; andcooling the second portion.
 12. The method according to claim 11 whereinsaid increased temperature of the second portion is approximately 100°C. and said period of time is a few minutes.
 13. The method according toclaim 11 wherein said step of heating the second portion includesdipping the second portion into boiling water.
 14. The method for makinga catheter having an elongated polymeric tube secured to means forintroducing fluid into or for receiving fluid from the elongatedpolymeric tube, the method comprising;forming an elongated, fuseless,polymeric tube having a lumen therein; placing the elongated polymerictube on a support mandrel; heating one portion of the elongatedpolymeric tube to an elevated temperature greater than 100° C. but lessthan the melting point of the polymeric tube for a sufficient time toeffect solid state polymerization of said one portion of the elongatedpolymeric tube; maintaining another portion of the elongated polymerictube at a temperature lower than said one portion during the time saidone portion is being heated so as to inhibit solid state polymerizationin said other portion; and removing the elongated polymeric tube fromthe mandrel, whereby an elongated fuseless polymeric catheter may beprovided having said one portion which exhibits kink and burstresistance and said other portion which is more pliable than said oneportion.
 15. The method according to claim 14 wherein the step offorming includes extruding the elongated, fuseless, polymeric tube, saidone portion of the tube being a body portion and said other portion ofthe tube being a tip portion.
 16. The method according to claim 14wherein said lower temperature of the other portion is sufficiently lowto prevent substantial solid state polymerization of the other portion.17. The method according to claim 14 wherein said lower temperature ofthe other portion is less than 80° C.
 18. The method according to claim14 wherein said lower temperature of the other portion is roomtemperature or below.
 19. The method according to claim 14 wherein thestep of heating the one portion includes subjecting the one portion ofthe elongated polymeric tube to a temperature zone greater than 100° C.but less than the melting point of the polymeric tube.
 20. The methodaccording to claim 19 wherein the other portion of the elongated tube issubjected to a lower temperature zone than said one portion.
 21. Themethod according to claim 14 wherein the step of heating includessubjecting the one portion of the elongated polymeric tube to anelevated temperature zone greater than 100° C. but less than the meltingpoint of the polymeric tube and wherein the elevated temperature zoneexhibits a pressure that is substantially lower than atmosphericpressure.
 22. The method according to claim 14 wherein the supportmandrel is a heat conductor which assists in distributing heat to theone portion of the polymeric tube.
 23. The method according to claim 14wherein the polymeric tube is formed of polyamide material.
 24. Themethod according to claim 14 including the steps of:forming the otherportion into a selected shape; heating the other portion to an increasedtemperature for a sufficient period of time such that the other portionwill retain the selected shape when cooled, said increased temperatureand period of time being insufficient to cause substantial solid statepolymerization of the other portion; and cooling the other portion. 25.The method according to claim 24 wherein said increased temperature ofthe other portion is approximately 100° C. and said period of time is afew minutes.
 26. The method according to claim 24 wherein said step ofheating the other portion includes dipping the other portion intoboiling water.
 27. The method for making a catheter having a fuseless,one-piece body and tip portion and being free of separate reinforcementfor the body, the catheter when in use being suitable for rapidlyintroducing pressurized fluids into the human bloodstream, the methodcomprising:precision forming an elongated, fuseless, thin-walledpolymeric tube of material comprising polyamide material, the tubehaving a lumen throughout its length and being of fuseless, one-piececonstruction, free of separate reinforcement; placing the elongatedpolymeric tube on a support mandrel having a selected shape; heating agenerally elongated body portion of the polymeric tube to an elevatedtemperature greater than 100° C. but less than the melting point of thepolymeric tube for a sufficient time to effect solid statepolymerization of said body portion of the polymeric tube; maintaining atip portion of the elongated polymeric tube at a temperaturesufficiently lower than said body portion during the time said bodyportion is being heated so as to inhibit solid state polymerization ofthe tip portion and provide a tip portion which is more pliable than thebody portion; and removing the polymeric tube from the mandrel, wherebya catheter may be provided having a body portion which is kink and burstresistant and a tip portion which is more pliable and atraumatic tipportion.
 28. The method according to claim 27 wherein said lowertemperature of the tip portion is less than 80° C.
 29. The methodaccording to claim 27 wherein said lower temperature of the tip portionis room temperature or below.
 30. The method according to claim 27wherein the step of heating the body portion includes subjecting thebody portion of the elongated polymeric tube to a temperature zonegreater than 100° C. but less than the melting point of the polymerictube.
 31. The method according to claim 30 wherein the tip portion ofthe elongated tube is subjected to a lower temperature zone than saidbody portion.
 32. The method according to claim 27 wherein the step ofheating includes subjecting the body portion of the elongated polymerictube to an elevated temperature zone greater than 100° C. but less thanthe melting point of the polymeric tube and wherein the elevatedtemperature zone exhibits a pressure that is substantially lower thanatmospheric pressure.
 33. The method according to claim 27 wherein themandrel is a heat conductor which assists in distributing heat to thebody portion of the polymeric tube.
 34. The method according to claim 27including forming the tip portion into a selected shape;heating the tipportion to an increased temperature for a sufficient period of time suchthat the tip portion will retain the selected shape when cooled, saidincreased temperature and time period being insufficient to causesubstantial solid state polymerization in the tip portion; and coolingthe tip portion.
 35. The method according to claim 21 wherein saidincreased temperature of the tip portion is approximately 100° C. andsaid period of time is a few minutes.
 36. The method according to claim34 wherein said step of heating the tip portion includes dipping the tipportion into boiling water.